Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$246.67	6.434%	$262.5407	$262.54	$262.55	$262.50
Purchase #2	$95.35	5.774%	$100.8555	$100.86	$100.85	$100.90
Purchase #3	$43.38	5.141%	$45.6102	$45.61	$45.60	$45.60
Purchase #4	$50.82	4.724%	$53.2207	$53.22	$53.20	$53.20
Purchase #5	$67.88	4.840%	$71.1654	$71.17	$71.15	$71.20
Purchase #6	$237.52	6.512%	$252.9873	$252.99	$253.00	$253.00
Purchase #7	$138.77	9.704%	$152.2362	$152.24	$152.25	$152.20
7 purchase totals =	$880.39		$938.6160	$938.63	$938.60	$938.60